1. Technical Field
The present invention relates to a power supply stabilizing circuit, an electronic device and a test apparatus. More particularly, the present invention relates to a power supply stabilizing circuit for stabilizing a power supply voltage to be supplied to an operational circuit of an electronic device, an electronic device with the power supply stabilizing circuit built-in, and a test apparatus using the power supply stabilizing circuit.
2. Related Art
To stabilize a power supply voltage to be supplied to an operational circuit of an electronic device such as a semiconductor circuit, it is known in the art to connect a pass capacitor to a power supply interconnection, for example, as disclosed in Japanese Patent Application Publication No. 07-333249. The pass capacitor is generally positioned, outside the chip of the electronic device, between the power supply interconnection that supplies power to the electronic device and the ground potential.
The pass capacitor reduces the variation in the current flowing through the power supply interconnection by supplying a current determined in accordance with the variation in the consumption current of the electronic device, to the electronic device via a power supply input terminal. In this way, the pass capacitor can reduce the variation in the power supply voltage due to the variation in the current. Generally, the pass capacitor used in the above manner has a capacitance of approximately several dozen nF to several μF.
Here, the power supply voltage may vary according to the variation in the consumption current of the operational circuit, also in the interconnection between the power supply input terminal of the electronic device and the operational circuit. This variation in the power supply voltage cannot be compensated for by the pass capacitor provided outside the chip of the electronic device.
To solve this issue, a similar pass capacitor may be provided also within the chip of the electronic device. To realize such a capacitor within the chip of the electronic device, the gate capacitance of a transistor may be utilized. A single transistor, however, has a gate capacitance of approximately several fF. Therefore, a very large number of elements need to be formed to implement a pass capacitor within the chip.